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The Downside of Treadmill Desks

A Google employee on a treadmill desk in February 2014.Credit Jim Wilson/The New York Times

Treadmill desks are popular, even aspirational, in many offices today since they can help those of us who are deskbound move more, burn extra calories and generally improve our health.

But an interesting new study raises some practical concerns about the effects of walking at your workspace and suggests that there may be unacknowledged downsides to using treadmill desks if you need to type or think at the office.

The drumbeat of scientific evidence about the health benefits of sitting less and moving more during the day continues to intensify. One study presented last month at the 2015 annual meeting of the American College of Sports Medicine in San Diego found that previously sedentary office workers who walked slowly at a treadmill desk for two hours each workday for two months significantly improved their blood pressure and slept better at night.

But as attractive as the desks are for health reasons, they must be integrated into a work setting so it seems sensible that they should be tested for their effects on productivity. But surprisingly little research had examined whether treadmill desks affect someone’s ability to get work done.

So for the new study, which was published in April in PLOS One, researchers at Brigham Young University in Provo, Utah, recruited 75 healthy young men and women and randomly assigned them to workspaces outfitted with a computer and either a chair or a treadmill desk.

The treadmill desk was set to move at a speed of 1.5 miles per hour with zero incline.

None of the participants had used a treadmill desk before, so they received a few minutes of instruction and practice. Those assigned a chair were assumed to be familiar with its use.

Then the volunteers were asked to complete a series of tests of their manual and mental dexterity.

The manual task was simple enough, consisting of using the keyboard to type words that flashed onto the computer screen as quickly and accurately as possible while the volunteer either sat or slowly walked.

The cognitive tests were more demanding, designed to measure practical aspects of cognition, such as working memory and delayed recall, and the ability to concentrate, all of which are important in performing office work. In one of these tests, volunteers had to learn and later recall lists of words; in another, they were asked to juggle lists of numbers and add them up in their heads even as new numbers were added to the list, possibly triggering unsettling flashbacks to high school algebra exams.

The results, when the researchers compared the treadmill walkers with the people sitting at their desks, substantially favored sitting. The people who had walked during the testing performed worse on almost all aspects of thinking, including the ability to concentrate and remember, compared with those who had been seated.

And they were much worse at typing, being substantially slower and more error prone than the sitting group.

No one should be surprised by this deterioration of typing ability while using a treadmill desk, said Michael Larson, a professor of psychology and neuroscience at B.Y.U. who led the study. “You’re not stationary,” he said. Even if the oscillation in your body position is slight, you are moving first closer to and then farther from your keyboard. “It’s like typing while rowing,” he said.

But the lower cognitive scores among the treadmill walkers, compared with people in chairs, were unexpected, Dr. Larson said. Most studies of the effects of physical activity on cognition show that moving improves thinking.

Dr. Larson noted that those studies generally had focused on the effects of thinking after someone had walked or otherwise moved around, not on how well people think while actually moving.

In the current study, he said, it appears that using a treadmill desk sopped up some of the volunteers’ available cognitive resources. By devoting a portion of their thinking to keeping themselves balanced on the treadmill, they became marginally less able to reason and remember.

This was a very limited, one-time test of people’s performance while using a treadmill desk or staying seated. It is extremely likely, Dr. Larson said, that if people repeatedly use a treadmill desk, they become accustomed to its effects and get better at walking, typing and thinking simultaneously.

It is also worth emphasizing, Dr. Larson said, that the cognitive performance of the treadmill-desk volunteers, while worse than that of the people in chairs, “remained within what would be considered normal” on all of the tests. They didn’t forget how to add. They just weren’t quite as adept as people who sat.

The upshot, Dr. Larson said, is that someone considering a treadmill desk should plan on a period of adjustment and might have to deal with lingering effects on typing and possibly even thinking.

But even with that caveat, he said, he believes that the health benefits of a treadmill desk should outweigh any declines in productivity and, in fact, he plans to buy one for himself.

A version of this article appears in print on 06/16/2015, on page D6 of the NewYork edition with the headline: A Treadmill Desk Balance.